Various vehicles, including long haul semi trucks, short haul semi trucks, L.T.L. trucks, boats, recreational vehicles, police vehicles, fire trucks, ambulance vehicles, various aircraft such as airplanes and helicopters and utility vehicles are equipped with electronic equipment. The electronic equipment requires power when the engine is running as well as when the engine shut off. The electronic equipment may include any combination or all of lighting, heating, cooling, refrigerator, microwave, toaster, coffee maker, TV., gaming system, and laptop computers. The use of electricity in a vehicle to power this electronic equipment is referred to as a “hotel load”. Regulations on idling engines, fuel consumption costs, emission of pollutants, engine wear, make it undesirable to run the engine to supply power for the hotel loads. Due to increased regulations over the years, many attempts have been proposed to supply power to the hotel loads while the vehicle engine is shut off.
At this present time, there are a couple different ways proposed to deal with powering the hotel loads while the vehicle engine is shut off. These current solutions include:
(1) Auxiliary power units (APU) powered by gasoline or diesel fuel;
(2) Vehicle's batteries—either the existing batteries or via extra batteries installed on the vehicles which are dedicated to powering the hotel loads;
(3) Electrically connecting the vehicle to an external AC power outlet (known as (“shore power”).
Certain Disadvantages and Draw Backs Remain with Respect to these Arrangements Currently Available with APUs, Extra Batteries Bank, and the Shore Power Based Electrical Power Systems.
The type of APU most commonly used is an engine-driven APU generator that utilizes diesel or other fuel such as gasoline or liquid petroleum. Such APUs provide an immediate source of electrical power, however, the electrical power the APU generates typically limited due to the small engine size used to power the APU. Thus, the sizing of the APU alternator is limited due to the horse power of the APU engine. The APUs typically used today are not designed to put out enough power to run all of the hotel loads, and charge the batteries to a sufficient state of charge when the vehicle is shut off. APUs are noisy and expel pollutants into the atmosphere. Some states have passed laws that the APUs must have a D.P.F. (“Diesel Particulate Filter”) added to the exhaust system of the APU to operate. Further conventional APUs are relatively heavy, have a relatively high initial cost and can be expensive to maintain.
Shore powered systems are superior to the use of an APU from the stand point of initial cost, weight, maintenance considerations and noise. However, a conventional power outlet may not be available where the vehicle operator either needs to, or is required to stop.
The use of the vehicle batteries to supply hotel loads, primarily consist of wiring to interconnect DC powered hotel loads to the vehicle batteries and an inverter unit for transforming DC current drawn from the batteries, to AC current for the AC powered hotel loads. These systems also are superior to the use of an APU from the standpoint of initial cost, weight, maintenance considerations, and noise. However, existing systems powered solely by the vehicle batteries are not capable of supplying the needed amount of current for the vehicle hotel loads for a sufficient or desired period of time without discharging the vehicle batteries to a point at which the vehicle cannot be started. Furthermore, the vehicle charging systems today, when the vehicle engine is running, are not adequate to continually charge the batteries to a high of 95%-100% state of charge. This is because current designs use lighter AWG (American wire gage, also known as Brown & Sharp wire gage) and tend to minimize the length of the wires to keep overall weight to a minimum for fuel consumption purposes. Wire length is minimized by using various techniques such as using the vehicle's frame as a ground such that a wire needs only to run from a component such as an alternator to the nearest open spot on the frame, or connecting different components like the alternator and the starter in series, such that the wires from each component need not extend from the battery all the way to each component.
For this reason, most of these types of over the road trucks have what is referred to as “low voltage disconnect,” or LVD switches. The purpose of these switches is to monitor the voltage of the vehicle batteries so that when the voltage of the vehicle batteries get below the set voltage on the switch, typically around 12.3V, the LVD switch will disconnect the power from the hotel loads. This ensures the batteries have enough charge left in them to start the engine. Design constraints applicable to power systems for hotel loads are in part dictated today, by the vehicle in which the systems are employed. One very demanding situation is the design and implementation of such power systems for long haul trucks equipped with sleepers. The way long haul class 8 trucks equipped with sleepers are designed today, are not a reliable charging and hotel load design for these types of trucks that have a need to stop running but continue to provide power to the hotel loads for an extended period of time, on the order of 8-10 hours.
Powering the hotel loads with the engine idling, or periodically starting the truck to charge the vehicle batteries during stops of any duration often is not a viable option as the trucks are designed today with idle times for the vehicle batteries to charge a minimum of 2 hours or more multiple times during an extended stop. Specifically, a growing number of state and regional authorities are enacting “no idle” rules and regulations that limit how often the engine may be idled during a stop and the duration over which the engine can be idled. On the other hand, Federal legislation mandates ten continuous hours rest during a 24-hour period for commercial truck drivers.
No-idle regulations also complicate existing harsh design and operational constraints that apply to hotel load power systems for long haul trucks. For example, a system for providing hotel power in long haul trucks should be capable of operating reliably over a wide range of ambient temperatures (outside air temperature), such as 115° F. or more, to −20° F. or less. Reliable operation at sub-zero ambient temperatures can be difficult to achieve because the power capacity of the vehicle batteries is greatly reduced at low ambient temperatures. Until now, there has not been a system that can charge the vehicle batteries fast enough during the low ambient temperatures effectively. Regardless of ambient temperature, long haul trucks require hotel load power for required driver rest periods of ten hours or more while still being able to have adequate power to start the vehicle engine. In addition, it is desirable that the power system be capable of supplying hotel loads for a period of time that would exceed the rest period of 10 hours, should the truck be unable to resume a trip due to extreme weather conditions or other causes. This further helps drivers of long-haul trucks as they are able to sleep for longer periods of time without being interrupted by the truck starting and restarting throughout the night.
Although weight and maintenance considerations can be important with respect to other vehicles, they are of special significance with respect to power systems for long-haul trucks. Reduced weight means reduced fuel cost and less pollution, and in some cases, can mean increased load capacity. Added savings includes reduced maintenance cost, and shorter time to return on investment.
Although progress has been made, the prior progress has not fulfilled the need to have a battery-powered low maintenance, low cost, weight, efficient power system that provides reliable operation over a wide temperature range while simultaneously ensuring that electrical power is available for engine starting at low ambient temperatures and after extended periods of operation.